Abstract: NMDA receptors are ligand-gated ion channels that play a critical role in the function of the central nervous system and are involved in processes such as synaptic plasticity, learning, and memory. In addition to their physiological functions, NMDARs are also implicated in a number of neurological diseases and conditions, including ischemic stroke and epilepsy. The diverse roles that NMDA receptors fill make it critical that the function and regulation of these receptors are fully understood. The recent structures have provided insight into the architecture and end state structures of NMDA receptors providing a rich foundation for structure- dynamic investigation of the receptor which will allow for detailed investigations of all the conformational states that the protein explores. This is required as there are still several unanswered questions such as mechanism underlying partial agonism as well as mechanism of allosteric communication between the glutamate and glycine binding. Single molecule Frster Resonance Energy Transfer (smFRET) method is ideally suited for such investigations as it allows for the characterization of all the states that the proteins probes and dynamics of transitions between the states, which then can be correlated to the extensive functional information available for the receptor. The research proposed herein seeks to fill these important gaps in knowledge through two aims: to Determine the mechanism of partial agonism in the NMDA receptor and to Study the allosteric communication between the glutamate- and glycine-binding subunits of the NMDA receptor. The research proposed will provide a significant step forward in the understanding of the function and regulation of the NMDA receptor. This research pursuit, therefore, is in keeping with the stated mission of the NIGMS to support ?basic research that increases understanding of biological processes and lays the foundation for advances in disease diagnosis, treatment and prevention?.